FLOW CYTOMETRIC EVALUATION OF BONE-MARROW DIFFERENTIALS IN RATS WITH PHARMACOLOGICALLY INDUCED HEMATOLOGIC ABNORMALITIES

Previously, flow cytometric determination of peroxidase activity, cell size, and reactivity to lymphocyte antibodies were used to produce bo ne marrow differentials in untreated rats. In the present study, abnor mal hematologic profiles were induced with erythropoietin (EPO), recom binant murine stem cell factor (rm-SCF), granulocyte-macrophage stimul ating factor (GM-CSF), and cyclophosphamide (CP), Manual and how cytom etric data show-ed comparable levels of erythroid and myeloid hyperpla sia in EPO-and rm-SCF/GM-CSF-treated animals, respectively. In CP-trea ted animals, flow cytometric data revealed significant decreases in ce llularity at concentrations of CP greater than or equal to 5 mg/kg, In contrast, 20 mg/kg CP were necessary to induce microscopically appare nt hypoplasia in histologic bone sections, showing that the automated methodology was a more sensitive indicator of bone marrow hypocellular ity than was the more conventional manual method. Megakaryocyte counts were consistently higher by flow cytometer than by manual counts perf ormed on cytocentrifuge preparations made from the same cell suspensio ns but were similar to megakaryocyte counts performed on histologic se ctions of femur, indicating that the automated methodology produced a more accurate reflection of the megakaryocyte numbers, Induction of he matologic abnormalities in the present study showed that manual bone m arrow differentials can be replaced with the more efficient and reliab le how cytometric method in most preclinical toxicology studies. (C) 1 998 Wiley-Liss, Inc.